grain boundarymigration, and discontinuous precipitation associated with pronounced grain boundary sliding. A high dislocation density was also developed within the grains Creep fracture was intercrystalline occurring by the growth of wedge-type cracks from triple points on boundaries normal to the tensile stress. However the presence of dimples on the grain boundary surfaces was indicative of some ductility within the narrow soft region adjacent to the boundaries. These observations may account for the low ductility found in these alloys at low creep strain rates or low stress levels.